Feeding system for an inductive load from an energy source with variable power

ABSTRACT

A system is provided for the feeding of an inductive load, with electric power of continuous current, generated from an energy source and, more in particular, to a feeding system for a vibratory pump from solar or aeolic energy, which processes the electric power of continuous current supplied by a bank of solar cells or aeolic generator, in a compatible form, using a circuit of electronic command by digital micro controller, for the control and actuation of vibratory pump, independent of the electric power variations supplied by the sources as solar cells, due to the alterations in the level of solar radiation; or in aeolic generator, due to wind speed variations.

FIELD OF INVENTION

The present invention refers to a system for feeding of an inductive load starting from an energy source whose useful power varies regarding time.

BACKGROUND

In a preferential form of accomplishment, the present invention refers to a vibratory pump with electric power feeding of continuous current, generated by a bank of solar cells or an aeolic (wind) generator. More in particular, it is described a feeding system for a vibratory pump starting from solar or aeolic energy, which processes the electric energy of continuous current supplied by the bank of solar cells or aeolic generator, in compatible form, using an electronic circuit of command by digital micro-controller, for the control and the activation of the vibratory pump, independent of electric power variations supplied by the source, due to the alterations in the level of solar radiation or due to the wind speed variations.

It is known that the systems that use pumps activated from a motor of continuous current have the need to generate a minimum power for their operation. In particular, how much larger the system hydraulics pressure, larger the need of energy for the motor to reach a minimum rotation. In a normal application, the energy fluctuations, in function of the natural variables of solar radiation or wind speed, they make the system suffers continuous downtime (periods of low level of solar radiation or of wind). To eliminate or to reduce such effects, usually they employ great quantities of solar cells or larger power of aeolic generation, what increases the systems implantation cost. Another solution to overcome such inconvenient is the use of banks of supplemental batteries that store energy during the periods of low energy and transfer to the pump in order that this can reach enough level of energy for the departure. However, the cost involved with this solution makes it completely unfeasible.

Actuation systems of electromechanical pumps are also known. They process the electric power only supplied by the solar cells, and convert the energy in variables pulses and spaced regarding the level of solar radiation. These systems operate in analogical form, where the circuit signals are treated in direct form, not allowing to attend the variables to which ones the system is subject, without alterations in the electronic project; this carries circuit costs increase, it limits the system input power, does not allow the use of pumps of larger performance and does not allow its use in aeolic generators, due to the high power supplied by these equipments. The use of such technique carries to a reduction in the system revenue, increasing the installed power cost of solar cells by pumped liter. Beyond of this, the protection means for the circuit are onerous and inefficient, operating only with independent systems. An example of such a system is the described in Brazilian patent PI 8204205, filed on Jul. 16, 1982.

SUMMARY

Thus, a first goal of the present invention is to supply a feeding system for an inductive load from an energy source with a variable useful power, able to control the power supplied for the inductive load, as well as accommodate it to the needs of the inductive load.

Further, another goal of the present invention is to supply a feeding system for a vibratory pump, from a bank of solar cells or aeolic generator, able to solve the technical problems.

In particular, the present invention comprehends a feeding system for an inductive load, from an energy source with variable power, from the conversion in pulses of constant energy and spaced regarding the useful power supplied by the energy source (2) and without batteries use. The conversion is made by a bridge circuit, controlled by a digital micro controller depending on the system variables. Moreover, the feeding of the inductive load is made through a resonant circuit in series RCL, in which the inductive component is the inductive load itself. The interface between the energy source and the inductive load is accomplished by an actuation module, which comprehends: a capacitor bank, fed by the energy source; a circuit bridge between the said capacitor bank and a key; a digital micro controller, destined to control the circuit bridge, with basis in the system variables; and a resonant circuit RCL in series, comprehending a resistance, a capacitor and the said inductive load, destined to feed the inductive load itself.

In other words, the system consists in transforming the electric power of continuous current generated by the source, in alternating current with the biggest possible efficiency, from the conversion in pulses of constant energy and spaced regarding the useful power supplied by the energy source and without batteries use, allowing low maintenance and with the possibility to use a larger power of electric generation, with the consequent improvement in the performance of the inductive load. Due to the application of a digital micro controller to the electronic circuit, the technical solution allows several configuration setups without alteration of the electronic project, because it improves the operation parameters in function of system variables (time of capacitor load, source voltage level and current in the inductive load). The digital micro controller also provides protection to the system in dependent form with introduction of a “mosfet” (field effect transistor) type key, of low energy loss that turns off totally the energy for the SCR″ (solid state key).

BRIEF DESCRIPTION OF THE DRAWINGS

The object of the present invention will be better understood from the detailed description that follows in a way preferential of accomplishment, illustrating the implementation of the system of the invention in the actuation of a vibratory pump starting from a bank of solar cells, which is made with support in the enclosed illustrations, in which:

FIG. 1 illustrates an block diagram of actuation system of the present invention, with highlight for the activation module of the vibratory pump;

FIGS. 2A and 2B illustrate a circuit corresponding to the activation module, according to FIG. 1; and

FIGS. 3A to 3F illustrate the flow chart of the control software of the activation module, according to FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention concept is based on electric power transformation of continuous current generated by the energy source, in pulses, through a digital technique, that results in a larger control, with consequent low maintenance and system larger efficiency. The electric power conversion of continuous current supplied by the source is accomplished through a resonant circuit RCL in series, which is formed by a capacitor (P6) associate to the coil of inductive load (P5).

For a better comprehension of the concepts that govern the present invention, it is described below one of the possible forms of practice accomplishment of this, in which the energy source is represented by a bank of solar cells, while the inductive load is represented by a vibratory pump, this pump destined to pumping of water. Nevertheless the illustrative scope and not limiting of this accomplishment, the experts in the art will realize that the concepts and the materialization of this system can be employed equally in other applications. For example, the energy source can comprehend an aeolic generator, whose useful power varies regarding the wind speed, or can comprehend a generator connected to a water wheel, whose useful power varies regarding the water flux. Furthermore, the load to be fed by the system is an inductive load, just as, for example, a vibratory pump, within others.

FIG. 1 illustrates, in the form of a block diagram, the actuation system of a vibratory pump, according to the present invention. In FIG. 1, an actuation module 1 is indicated, which is connected to the energy source 2 and the vibratory pump P5.

The activation module 1 generally comprises a capacitor bank 11, a circuit bridge 10, a key 12, a capacitor P6 and a digital micro controller 20, which is responsible for the control of the whole energy transformation received from source 2 and of the feeding control supplied for the vibratory pump P5.

More particularly, the energy source input originating from the solar cells or aeolic generator 2 is driven to a capacitor bank 11, which stores the energy and supplies it to the bridge circuit 10. The capacitor bank 11 is connected to the digital micro controller 20 through a voltage sensor 14, which informs the digital micro controller 20 of the voltages in referred capacitor bank 11. The capacitor bank 11 has its output linked to the bridge circuit 10, which is controlled by digital micro controller 20 through actuators 15. The bridge circuit output 10 is linked to a key 12, comprised of four keys of solid state or SCRs, which in turn has its output connected to capacitor P6 and its actuation connected to an output of digital micro controller 20. The vibratory pump P5 is fed through capacitor P6 (forming the circuit RCL series) and it presents a current sensor 16 destined to inform to the digital micro controller 20 about the current intensity that traverses the inductive load (vibratory pump P5).

Finally, the digital micro controller 20 receives as inputs the signals coming from the voltage sensor 14 of capacitor bank 11, of the current sensor 16 of the vibratory pump P5 and of a delay selector 17. The controls made by digital micro controller 20 correspond to activation of actuators 15 of the circuit bridge 10, of the key 12, as well as information supply of the control through the fault LED (light emitting diode) 18 and pulse LED 19.

In operation, the activation module 1 receives a certain quantity of energy originating from the source 2, stores such energy in the bank of capacitors 11 and transforms this energy (as it will be described in greater detail below) through the bridge circuit 10. This energy thus transformed is converted (in 12) to alternating current and supplied for the vibratory pump P5, through capacitor P6. All control of operation of actuation module 1 is accomplished by means of digital micro controller 20, according to the illustrated routines, by way of example and not limiting, by the illustrations flowcharts FIGS. 3A to 3F.

In other words, the actuation module 1 is a circuit able to supply alternating current to the inductive load (vibratory pump P5) employing the energy stored in the electric field of capacitors 11. The energy conversion occurs by means of the alternating of current sense, via bridge circuit 10, in resonant series circuit, comprising capacitor P6 and inductive load (vibratory pump P5). Control of the bridge circuit 10 is accomplished by digital microcontroller 20, based on a digital processor, according to information from the sensor 14 voltage and current sensor 16, within the circuit.

System Overview

FIGS. 2A and 2B illustrate the circuit corresponding to the actuation module, according to the present invention. The activation of the series resonant circuit, composed by the capacitor (P6) and vibratory pump (P5) is given by the control of the presence and of the current sense via the circuit bridge.

For the circuit bridge command, the control system, implemented in digital micro controller (U2), evaluates the voltage level of the of energy storage capacitors (C14 and C15) of capacitor bank 11. This information originates from the voltage circuit sensor 14.

If a minimum level of voltage is detected, the current is allowed to circulate in just one of the two possible paths. It evaluates then the current intensity that passes trough the inductive load (vibratory pump P5). This information originates from the current circuit sensor 16.

If the current is within the programmed levels, the described sequence is repeated; however the circuit bridge 10 is commuted so that the current flows in the opposite direction.

Prior to reversing the direction, the current opens the electronic switch (Q9) capable of interrupting currents possibly remaining in the inductive load (vibratory pump P5) and timings with pre-programmed durations that take place, via software.

The timings values are defined as electric characteristics of the series resonant circuit.

During the timings the current circulation is prevented by the inductive load (vibratory pump P5).

Bridge Circuit Description and Series Resonant Circuit

The vibratory pump (P5), that is the load to be fed, with inductive characteristic, is in series with a capacitor (P6), resulting in a LC circuit. As is known, such circuits have an angular frequency of resonance given by:

$\omega_{0} = \frac{1}{\sqrt{LC}}$

If there were no losses, a stimulus in this circuit would provoke an oscillation of infinite duration, with frequency equal to the resonance. As there are losses, an impulse can provoke an absorbed oscillation, that is, with decreasing amplitude along time. In this case, the oscillation frequency is a bit different from ω_(o).

In the module circuit, the vibratory pump (P5) and the capacitor (P6) meet in the central branch of circuit bridge 10 controlled by thyristors (Q1, Q2, Q3 and Q4).

The devices Q1, Q2, Q3 and Q4 are responsible for the current sense in the LC circuit, commutating a pair diagonally opposed each time (Q1 and Q4, Q3 and Q2).

With this and reminding that the voltage in the inductor is obtained by

${v_{L}(t)} = {L\frac{{i(t)}}{t}}$

It is described, following, the alternating voltage obtainment about the inductor (vibratory pump P5).

At the moment in which the circuit is connected, the inductor and the capacitor are unloaded. Of the electric point of view the inductor is an open circuit and the capacitor is a short circuit.

Switching to a pair of thyristors diagonally opposed (Q1 and Q4) a current will start to run the LC circuit.

However, in a first instant, as the inductor is an open circuit, the current is null (note: it is not being considered, in this description, the starting current).

Little by little the inductor loads itself and stores energy in the form of a magnetic field. With that the inductor impedance starts to decrease, allowing a current increase. Conversely, the capacitor P6 also loads itself, when accumulating energy in form of electric field and, consequently, its impedance starts to increase. Then, summing the effect of inductor P5 and of capacitor P6, the resultant current increases just for a certain time interval, decreasing soon after.

Yet, the current when increasing, is increasing with decreasing rates of increment and, when decreasing, is decreasing with increasing rates of decrement. Because of this, when the current is increasing, a positive voltage will appear with decreasing amplitude along time (observe the derivative effect in the expression for ν_(L)(t)), until the current stop to increasing.

In this point, the voltage is null, because the punctual derivative of the current is null. Soon after, when the current becomes decreasing, it has as result a negative voltage with amplitude, in module, increasing (again, observe the expression for ν_(L)(t)). The current decreases until it reaches zero.

The time to current decrease depends on the characteristics of LC circuit and the associated losses.

The thyristors elements have characteristics to stop conducting at null or near to zero currents. In this instant, the current in the circuit is interrupted and the capacitor P6 is loaded with a certain voltage.

Some instants after, in accordance with the programmed timing in the control system, only the other pair of thyristors diagonally opposite (Q3 and Q2) are activated.

The inductor can be considered open and the current becomes to increase little by little, as already described, however in the opposite direction as before.

The capacitor, in turn, starts to unload itself and, soon after, is loaded with an opposite voltage. This way, the current, again, will reach a maximum and will decrease until it empties itself.

This will result in alternate voltage in the inductor, as previously, but with opposite value along time, regarding the previous case.

Again, when the current is null or near zero, thyristors stop conducting, interrupting the current in the circuit.

Finally, after pre-programmed timing in the control system, it commutes again the first pair of thyristors, and the cycle repeats, reminding that the capacitor will be always loaded before the commutation, except for the instant in which the activation module circuit 1 is connected.

The energy supplied by the source 2 to the system generates a current that crosses the capacitor and starts to flow through the inductor P5. When the inductor tends to its purely ohmic resistance, the capacitor will tend to an infinite resistance, which will make the current reach a value near zero; at this moment the capacitor will have accumulated the maximum possible of energy.

When the current is near zero a module formed by four SCRs which control the energy that will be generated for the vibratory pump P5, it will invert the current direction, and as the capacitor is energized it will be the sum of two voltages sources, one originating of the solar cells (source 2) and the other of the capacitors.

The SCR's control occurs through pulse transformers that isolate the discharges of electromagnetic interference of the remaining circuit.

To guarantee a better system performance a capacitor bank 11 is provided that accumulates energy originating from the solar cells 2, serving as auxiliary generator of energy, thus, the system operates with a minimum of solar radiation on the solar cells, in other words, low useful power.

The advantages of this system with regard to other existing systems is that this system includes a digital micro controller that optimizes its operation parameters in function of system variables: capacitor load time, voltage level source and system current level, which allows the use of a larger installed power of generation, improving the hydraulic performance of the vibratory pump. This digital micro controller 20 protects the system against eventual faults and allows for parameterization, making thus the adjustment more efficient the maximum performance curves of the vibratory pumps (pressure x flow).

Since the system can work in places with few resources and operationally inhospitable, safety devices were introduced to attend the requisites programmed in digital micro controller, so that they return to operation automatically, in the event that the system presents a temporary failure. These devices are of two types: dependent on digital micro controller intervention and totally independent. For the dependent system, a key type low energy loss mosfet was introduced, which completely turns off the energy to the SCR. The independent system is constituted by a protection device of counter current, over current and current (fuse).

As mentioned above, FIGS. 3A to 3F illustrate the software flow chart control actuation module, in order to exemplify to a possible form of referred module 1. It should be highlighted, however, that the variables described (time, current, tension, etc.) are merely illustrative and applicable in function of energy source and of the inductive load have be fed and controlled. For specific applications, one of ordinary skill in the art is able to perform the necessary alterations without deviating from the scope of the invention.

As a result of the above description, it can be verified that the system, object of present invention, is very versatile, as well as allowing feeding and efficient control of the inductive load by this feed.

The electric power source can be comprised of one or more solar cells, one or more aeolic generators, one or more generators coupled to water wheels, as well as for other similar systems, whose main characteristic is an inconstancy in the supplied useful power. Such characteristic of the invention aim to expand the utility range, mostly of the electric generators based on natural resources, whose use is developing rapidly. In another accomplishment form, the generator of electricity source can be of chemical action, by cells or batteries. In another embodiment, the generator source of electricity can be by induction, as by generators or dynamos, coupled to hydraulic turbines or to other energy sources that enable its activation.

Conversely, the load to be fed and controlled by the system, in function of the formation of the resonant circuit RCL, there necessarily should be an inductive load, as in the vibratory pump described above. It should be clear, however, that other loads can be fed by the present inventive system, since they present the same condition.

Finally, the current control supplied for the load is accomplished by digital micro controller, which can be configured for each specific use, without change in its circuit. As a result, the system is versatile for several applications, thus reducing production cost in scaling. Furthermore, the load feeding control is very efficient and is accomplished by the system variables control, which time of capacitor load, the source voltage level and the current level of the inductive load. With base in the accompaniment of these variables, the micro controller fits itself as to keep an optimized condition regardless of the useful power supplied by the energy source and the load use condition. In addition, the digital micro controller also provides protection for the system, in a dependent form, from a mosfet key of low energy loss, which completely turns off the energy to the SCR. 

1. A feeding system for an inductive load from a variable power energy source, that converts into pulses of constant energy and spaced according to useful power supplied by the energy source (2) and without use of batteries, wherein the conversion is performed by a circuit bridge (10), controlled by a digital micro controller (20) as a function of system variables, and the feeding of the inductive load is accomplished through a resonant circuit in series RCL, in which the inductive component is the inductive load itself (P5).
 2. The system, according to claim 1, wherein the interface between the energy source (2) and the inductive load (P5) is performed by an actuation module (1), which comprises: a capacitor bank (11), fed by the energy source (2); a bridge circuit (10) disposed between the capacitor bank (11) and a key (12); a digital micro controller (20), destined to control the bridge circuit (10), based on the system variables; and a resonant circuit RCL in series, comprising a resistance, a capacitor (P6) and the inductive load (P5), destined to feed the inductive load itself (P5).
 3. The system, according to claim 1, wherein the system variables comprise: voltage supplied by the energy source (2), measured by a voltage sensor (14); current in the inductive load (P5) measured by a current sensor (16); and load time of a capacitor (P6).
 4. The system, according to claim 2, wherein the micro controller (20) acts on the bridge circuit (10) through actuators (15), as well as acting on the key timing (12).
 5. The system, according to claim 2, wherein the digital micro controller (20) also provides protection to the system, in a dependent form, starting from a key type mosfet (poMFET) of low energy loss, which is placed between said digital micro controller (20) and the key (12), so as to completely turn off the energy for SCRs of the key (12).
 6. The system, according to claim 1, wherein the energy source (2) comprises one or more solar cells.
 7. The system, according to claim 1, wherein the energy source (2) comprises one or more aeolic generators.
 8. The system, according to claim 1, wherein the inductive load (P5) comprises one or more vibratory pumps.
 9. The system, according to claim 1, wherein the energy source (2) comprises electricity generation by magnetic induction.
 10. The system, according to claim 1, wherein the energy source (2) comprises electricity generation produced by chemical action.
 11. A feeding system for a vibratory pump from solar cells, from conversion into pulses of constant energy and spaced regarding useful power supplied by the solar cells (2) and without use of batteries, wherein the conversion is performed by a bridge circuit (10), controlled by a digital micro controller (20) as a function of system variables, said variables comprising: voltage supplied by the solar cells (2), measured by a voltage sensor (14); current in a vibratory pump (P5) measured by a current sensor (16); and time of capacitor load (P6), the feeding of the vibratory pump (P5) is performed by a resonant circuit in series RCL, in which the inductive component is the pump itself (P5), and an interface between the solar cells (2) and the vibratory pump (P5) is performed by an actuation module (1), which comprises: a capacitor bank (11), fed by the solar cells (2); a bridge circuit (10) disposed between capacitor bank (11) and a key (12); a digital micro controller (20), that controls the bridge circuit (10), based on the system variables; and a resonant circuit RCL in series, comprising a resistance, a capacitor (P6) and the vibratory pump (P5), that feeds the vibratory pump itself (P5).
 12. The system, according to claim 11, wherein the micro controller (20) acts on the bridge circuit (10) through actuators (15), as well as acting in the key timing (12).
 13. The system, according to claim 11, wherein the digital micro controller (20) also provides protection to the system, in dependent form, from a mosfet type key (poMFET) of low energy loss, which is disposed between the digital micro controller (20) and the key (12), so as to completely turn off the energy of SCRs to the key (12). 